Recombinant and synthetic nucleic acids have many applications in research, industry, agriculture, and medicine. Recombinant and synthetic nucleic acids can be used to express and obtain large amounts of polypeptides, including enzymes, antibodies, growth factors, receptors, and other polypeptides that may be used for a variety of medical, industrial, or agricultural purposes. Methods for screening of polypeptides with a predetermined function or property have been described, including phage display. However, current screening methods are limited by the size of the libraries, the lengths and complexities of polypeptides and available functional assays.